<i>Bb</i> preserves the integrity of HT29-19A epithelial cells.

<p>Filter-grown HT29-19A monolayers were treated with 10 ng/ml TNFα with or without live <i>Bb</i> placed in the apical compartment for 4 h. As index of epithelial viability, we measured markers of apoptosis (M30) and epithelial tight junction integrity (ZO-1). After 4 hour-treatment with <i>Bb</i>, HT29-19A monolayers (Costar® clear 3460) were labelled with the monoclonal antibody M30 CytoDEATH recognizing caspase-cleaved cytokeratin 18 (1∶10, Roche Diagnostics) and rabbit polyclonal anti-ZO-1 (24 µg/ml, Zymed). Cells were observed with the laser scanning confocal microscope LSM 510 Carl Zeiss. Treatment with H₂O₂ (100 µM), used as a positive control, induced apoptosis (blue M30 labeling) and alteration of ZO-1 distribution (green). In contrast, in basal condition or after treatment with <i>Bb</i> at MOI 100, no M30 labeling was observed and ZO-1 distribution was preserved. Results are representative of three independent experiments.